#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>

int main()
{
	double ant = 0;
	double len = 5;
	double div = 0;
	int day = 0;
	while (1)
	{
		ant++;
		div = ant / len;
		len = len + 5;
		ant = len * div;
		day++;
		if (ant >= len)
			break;
	}
	printf("%d", day);

	return 0;
}